1. Field of the Invention
The present invention relates to a cassette assembly for storing a plurality of wafer units including semiconductor wafers, for example.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines called streets are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby partition a plurality of regions where a plurality of semiconductor devices such as ICs and LSIs are respectively formed. The semiconductor wafer is cut along the streets by a processing apparatus such as a cutting apparatus and a laser processing apparatus to thereby obtain the individual semiconductor devices.
The processing apparatus mentioned above includes workpiece holding means for holding a wafer unit formed by attaching a wafer to a dicing tape supported to an annular frame, processing means for processing the wafer of the wafer unit held by the workpiece holding means, feeding means for relatively moving the workpiece holding means and the processing means in a feeding direction, a cassette table for mounting a cassette storing a plurality of wafer units, and transfer means for transferring the wafer units stored in the cassette mounted on the cassette table to the workpiece holding means.
The cassette for storing a plurality of wafer units includes a first side wall and a second side wall arranged parallel to the first side wall with a predetermined space defined therebetween. A plurality of frame supporting grooves are formed on the inner surface of each of the first and second side walls in such a manner that the frame supporting grooves of the first side wall are respectively opposed to the frame supporting grooves of the second side wall. The opposite side portions of the annular frame constituting each wafer unit is inserted into any opposed ones of the frame supporting grooves of the first and second side walls and placed on the lower surfaces of the opposed frame supporting grooves, thereby storing each wafer unit in the cassette. The cassette as configured above has a capacity of storing about 25 wafer units in consideration of the operating efficiency of the processing apparatus (see Japanese Patent Laid-open No. 2000-91411, for example).